The noise characteristics of inverted velocity profile coannular jets
Abstract
Measurements have been made of the noise of inverted velocity profile coannular jets (outer greater than inner velocity), statically at model scale. It has been found that an annular jet has both jet mixing and shock-cell noise lower than a round jet and that this benefit is increased when flow is added to the centre of the jet. Consideration of potential applications shows that for a conventional turbofan with a large temperature differential between the streams, inverting the flows always gives lower noise but that this is rarely less than that of a single stream jet of the same thrust and massflow. When both streams are hot and of a similar temperature, however, the inverted profile jet is always quieter. Reductions in peak noise of up to 4PNdB have been found, but due to the limited angular range of the benefit are estimated to be worth less than 2EPNdB in flight.
- Publication:
-
American Institute of Aeronautics and Astronautics Conference
- Pub Date:
- October 1977
- Bibcode:
- 1977aiaa.confQ....C
- Keywords:
-
- Aeroacoustics;
- Aerodynamic Noise;
- Annular Flow;
- Jet Aircraft Noise;
- Noise Measurement;
- Airspeed;
- Flow Velocity;
- Jet Mixing Flow;
- Temperature Effects;
- Turbofan Engines;
- Velocity Distribution;
- Acoustics